Hydrocarbon polymers, particularly ethylene-alpha olefin copolymers, are in widespread use as viscosity index (V.I.) improving additives for oil compositions, particularly lubricating oil compositions. A substantial body of prior art exists directed towards further reacting these ethylene-alpha olefin copolymer V.I. improvers to form a multi-functional V.I. improver. This dispersant V.I. Improver additive is used to improve not only the V.I. properties of the oil but to also impart dispersancy so as to suspend soot or sludge that may form during the operation or use of the lubricant in engines. Various patents teach grafting ethylene-alpha olefin copolymers with maleic anhydride, followed by reaction with an amine. A number of these prior disclosures teach reducing or avoiding the use of polyamine having two primary amine groups to thereby reduce cross-linking problems which become more of a problem as the number of amine moieties added to the polymer molecule is increased in order to increase dispersancy. Generally, these patents used a primary-tertiary amine.
U.S. Pat. No. 4,160,739, issued Jul. 10, 1979, to Stambaugh et al. discloses graft copolymers wherein the backbone polymer is a polymeric hydrocarbon such as substantially linear ethylene-propylene copolymer and the grafted units are the residues of a monomer system comprising maleic acid or anhydride and one or more other monomers copolymerizable therewith, the monomer system being post-reacted with a polyamine compound comprising a primary or secondary amine. The graft copolymers impart combined, detergent, viscosity index improvement and other useful properties to lubricating oils and hydrocarbon motor fuels.
U.S. Pat. No. 4,735,736, issued Apr. 5, 1988, to Chung discloses oil-soluble ethylene-alpha olefin hydrocarbon polymers, useful as V.I. improvers, such as ethylene-alpha olefin copolymer, preferably ethylene-propylene copolymer, grafted with an unsaturated acid material, such as maleic anhydride, preferably by solid state grafting followed by reaction with a polyamine, preferably a tertiary-primary amine, and treatment and/or reaction with aliphatic monoamine. The resulting material is used in oil compositions, such as lubricating oil, as a viscosity index improver having sludge dispersancy properties. The monoamine treatment inhibits viscosity growth of the additive upon storage.
U.S. Pat. No. 4,863,623, issued Sep. 5, 1989, to Nalesnik discloses an additive composition comprising a graft and an amine-derivatized copolymer prepared from ethylene and at least one C3 to C10 alpha-monoolefin and, optionally, a polyene selected from non-conjugated dienes and trienes comprising from about 15 to 80 mole % of ethylene, from about 20 to 85 mole % of the C3 to C10 alpha-monoolefin and from about 0 to 15 mole % of the polyene having a average molecular weight ranging from about 5,000 to 500,000 which has been reacted with at least one olefinic carboxylic acid acylating agent to form one or more acylating reaction intermediates characterized by having a carboxylic acid acylating group within their structure and reacting the reaction intermediate with an amino-aromatic polyamine compound from the group consisting of an N-arylphenylenediamine, an aminothiazole, an aminocarbazole, an aminoindole, an aminopyrrole, an amino-indazolinone, an aminomercaptotriazole and an aminopyrimidine to form the graft and amine-derivatized copolymer. A lubricating oil composition containing the amine-derivatized copolymer is also disclosed.
U.S. Pat. No. 5,429,757, issued Jul. 4, 1995, and U.S. Pat. No. 5,563,118, issued Oct. 8, 1996, to Mishra et al. disclose an additive composition comprising a graft and derivatized copolymer prepared from ethylene and at least one C3 to C10 alpha-monoolefin and, optionally, a polyene selected from non-conjugated dienes and trienes comprising from about 15 to 80 mole % of ethylene, from about 20 to 85 mole % of the C3 to C10 alpha-monoolefin and from about 0 to 15 mole % of the polyene having an average molecular weight ranging from about 5,000 to 500,000, which has been reacted with at least one olefinic (carboxylic acid acylating agent to form one or more acylating reaction intermediates characterized by having a carboxylic acid acylating group within their structure and reacting the reaction intermediate with an amino-aromatic compound to form the graft derivatized copolymer.
U.S. Pat. No. 6,107,257, issued Aug. 22, 2000, to Valcho et al. discloses a additive comprising a highly grafted, multi-functional olefin copolymer comprising a graft and amine-derivatized copolymer prepared from ethylene and at least one C3 to C23 alpha-monoolefin and, optionally, a polyene, wherein the copolymer of ethylene and at least one C3 to C23 alpha-monoolefin has grafted thereon from 0.3 to 0.75 carboxylic groups per 1,000 number average molecular weight units of olefin copolymer and wherein the olefin copolymer has a number average molecular weight of between 20,000 and 150,000.